Tribological behavior of Ti–6Al–4V alloy: Subsurface structure, damage mechanism and mechanical properties

Abstract

This paper describes the wear behavior, subsurface damage mechanism with structural change and indentation creep of bioinert Ti–6Al–4V alloy at different applied loads. Wear test was carried out on a pin-on-disk tribometer and their subsurface damage and deformation mechanism induced by a dry contact sliding were examined by SEM, EBSD and TEM techniques. A microstructural analysis revealed that a very fine β-Ti phase is evenly distributed in the α-Ti matrix. Consequently, the elastic modulus and microhardness of the alloy displayed 107.3 GPa and 324 HV, respectively at room temperature. However, the elastic modulus of Ti-alloy dropped approximately 35.4% at 700 °C. On the other hand, during the pin-on-disk test, severe loose fragments and delamination or plunged groove were observed at the edge of the overall wear tracks, causing abrasive wear. Under a low load, microcracks appeared beneath at the wear track. As increasing the load, the gross plastic deformation and severe microcracks emerged at the worn surface and soften the matrix due to frictional heat, leading to an accelerated wear rate. However, at the worn subsurface recrystallisation phenomena occurred. The grain size reduced and the nanohardness and elastic properties increased.